Why Does Swiss Cheese Have Holes?
Bacteria cause the holes in Swiss cheese. Like all cheeses, Swiss cheese is made by separating the solid part of milk (or curd) from the watery part, and pressing the curd into a solid cake. During the process of making Swiss cheese, a special kind of bacteria is also added to the milk to develop the sweet flavor of the cheese.
It is the action of these bacteria that also gives Swiss cheese its unique appearance. As the cheese is curing, the bacteria give off gas. The gas bubbles form the familiar round holes, or “eyes,” of the cheese. Recently this theory is being debated by the scientists in Switzerland who say they have finally solved the mystery of the holes in Swiss cheese.
Agroscope, a Swiss agricultural institute, believes that tiny specks of hay are responsible for the holes in Swiss cheese. These microscopically small hay particles fall into buckets of collected milk, then cause holes to form in the cheese as it ages. As modern milking methods have become more automated and antiseptic, and less hay particles drop into the milk, the number of holes in Swiss cheese has declined.
The holes in Swiss cheese have created trouble in the past for commercial cheese producers. In 2000, the FDA regulated the holes in Swiss cheese to be between 3/8 and 13/16 of an inch in diameter because newer cheese slicing equipment was tearing large-eyed Swiss cheese apart.